Differential diagnosis of renal tumours with clear cell histology.

Clear cell renal cell carcinoma is the most common malignant renal epithelial tumour and constitutes 90% of cases that metastasise. Nevertheless, it is important to recognise that not all clear cell carcinomas contain a preponderance of clear cells and that other renal tumours with different biologies and sensitivities to systemic therapeutic agents may exhibit clear cell cytology. Close attention to the cytological and growth pattern characteristics will allow us to arrive at the proper diagnosis, sometimes with the aid of immunohistochemistry.